1. Field of the Invention
This invention relates to latching mechanisms for stacked drawer arrangements, for example, in filing cabinets, which mechanisms act to allow withdrawal of only one drawer at a time. Such arrangements are intended to maintain the stability of the stack against tipping.
2. Description of the Prior Art
The provision of anti-tip latching arrangements has presented a large number of practical problems and a large amount of prior art exists. Generally, anti-tip mechanisms require great precision in installation of the anti-tip interactive components secured, for example, to a filing cabinet, and of the related actuating pins carried by the cabinet drawers.
Many conventional arrangements utilize vertical rigid bars, associated with the drawers. In one such conventional arrangement, each drawer is associated with a single vertical bar of similar height to the height of the respective drawer. Each bar is itself associated with a stop to prevent withdrawal of its associated drawer. The bars and their stops are positionable such that all the stops except one are located to block withdrawal of their respective drawers.
In the second conventional arrangement, each drawer is associated with a pair of vertical, rigid bars (split bars), each pair being associated with a stop for the respective drawer. The system works in a somewhat similar manner to that described for the first system, but this second system may be more versatile in that each stop may be located at the junction between bars of each pair and the length of each bar of the pair may be selected at will. Pratzer U.S. patent application Ser. No. 384,792 and assigned to the same assignee as the present invention, discloses and claims such a system.
Other patents representative of the art utilizing rigid bars are U.S. Pat. No. 4,768,844 issued Sept. 6th, 1988 to Ludwig and U.S. Pat. No. 4,429,993 issued February 1984 to Blouin.
Another known arrangement utilizes a flexible ribbon rather than rigid bars. When all the drawers are closed the ribbon has some slack in it. When one drawer is pulled in the opening direction a lug associated with the drawer actuates a cam to take up the slack of the ribbon to tauten it, and to allow the drawer to open. No further slack is available to be taken up by other similar cams associated with other drawers. The tautened ribbon blocks actuation of these other cams preventing opening of the associated drawers. Such an arrangement is described in U.S. Pat. No. 3,799,638 issued Mar. 26th, 1974 to Faiks which discloses a system in which the slack take-up mechanism is fixed in relation to the cabinet thus fixing the relative locations of the drawers. In practice, arrangements utilizing flexible ribbon have not been as widely used as those using rigid bars. One possible reason is that accuracy and reliability may have been less easy to achieve using a flexible ribbon which may be subject to stretching or elongation or contraction due to temperature related changes in length of the ribbon. Since very small lengths of slack have been permissible, change of length of the ribbon could be of significance.
The mechanisms of all the previous mechanisms known to the applicant have involved the provision of structure defining the location of drawers and cooperating structure on the drawers. It would be desirable to be able to rearrange the location or drawers, say drawers of different depths, without the need for any specialist procedures or the use of special tools.